Rheostat for electric lamps



T. A. LAGEY, RHBOSTAT FOR ELECTRIC LAMPS.

( No Model.)

Patented 00tf2'7, 1891.

UNITED STATES PATENT ()EEIcE.

THOMAS A. LACEY, OF PAUL, MINNESOTA.

RHEOSTAT FOR ELECTRIC LAMPS.

SPECIFICATION forming part of Letters Patent No. 4 62353, dated October 27, 1891.

Application filed May 5, 1891. Serial no. 391,687. (no model.)

To all whom, it may concern.-

Be it known that I, THOMAS A. LACEY, a citizen of the United States, residing at St. Paul, in the county of Ramsey and State of Minnesota, have invented certain new and useful Improvements in Rheostats for Electric Lamps; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

My invention relates to rheostats for electric lamps; and its object is to provide each separate or individual lamp with a rheostat which serves as such and also as a socket for the lamp, and which, when appliechwill serve for reducing the intensity of the current to any desired extent while admitting of its being of the usual intensity; and my invention consists in certain novel constructions, combinations, and arrangements of parts in a rheostat, whereby while its use is practicable as a combined socket and rheostat of a high resistance it can be made of such a size to be compact in form and not a source of danger from fire.

In the accompanying drawings, Figure l is an elevation of my improved combined rheostat and electrical lamp-socket, a portion of the outer case being broken out to indicate the interior construction. Fig. 2 is a side elevation of the interior portions of the rheostat removed from the case. Fig. 3 is a top view of the parts shown in Fig. 2. Fig. & is a vertical central section of the parts shown in Fig. 2. Fig. 5 is a horizontal section of the parts shown in Fig. 2, and Fig. 0 is also a horizontal section showing a modified form of resistancecoil.

Ain the drawings designates a brass cap or shell by which the outer cylinder or case B is secured to the flexible cord or fixture C. The socket or cylinder B is of brass, lined with asbestus or other suitableheat-resisting substance I), and it serves for inelosing the rheostat proper D, its lower end being extended in the form of a neck a, which forms the socket for an ordinaryincandescent electric lamp, and may be of any suitableknown construction to insure a perfect union between said lamp, rheostat, and the cylinder B. In the periphery of the cylinder IS a number of'holes b for ventilation are provided, the same extending entirely around the cylindcr.

E is a horizontal segmental ventilation opening or slot, in which the switch-bar F, to which the handle F is attached, moves to the right and left.

G is one of two small screws for binding the cylinder B to the cap A. The switch-plate F is made of hard rubber, fibrous or other non-conducting material, and maybe nearly two inches in diameter and one-quarter or one-eighth of an inch in thickness, or of such dimensions as found best.

H is the central binding-post with screw device 11, by which the switch-bar F is secured to the switch-plate F and on which it vibrates. The positive wire from the main is attached to this central post.

I and I are binding'posts at the termini of two insulated brass rods I I which convey the current to and from the lamp. Fig. 2 shows the direction of the current, the usual negative and positive signs being employed to show the connection of the negative and positive wires and the arrows to show the direction of the current when all the coils are in circuit. It will be evident from Fig. 3 that as the portion F of the switch-bar F moves toward the binding-post I the coils are successively cut out of the circuit.

K to K are small brass strips firmly secured to the switch-plate F in such a manner that theypresent a perfectly smooth surface, being embedded in the switch-plate F and thus insulated from each other.

K is a fuse-wire which conveys the current from K to the binding-post I.

The switch-bar F is of brass and is plainly shown in plan view and edge and sectional views in the drawings. It is operated by means of the handle F, which is on the end of the bar which projects through the slot E in the outer case or cylinder.

The handle proper F may be constructed of rubber or other non-conducting matertial, and the switch-bar should be arranged in such a manner as to slide easily, but with firm contact over the brass strips K to K This contact is maintained by the arching form of the bar, which gives a spring action to the switch between its downwardly bent end, which comes in contact with the strips and its shouldered portion, which rests on the switch-plate F as shown, pressure being produced on the middle of the spring switch-bar F by the central binding-post H, which, by being screwed into the plate, as shown in Fig/1t, insures the firmness of contact of the end Won the strips K to K that is requisite in the use of the rheostat. The brass strips to 70 are in series with each other and connected with the coils J, J, or J of the rheostat by wires leading to and from the coils, said wires being secured firmly to the said strips, and the last strip K being attached to the binding-post I by a fuse-wire K By referring to Figs. 3, a, and 5 the special construction of the rheostat will be seen. The rheostat-frame comp-rises two insulated brass rods I I for conveying the current to and from the lamp, and these rods at the switch-plate terminate in the binding-posts I I, the rod 1 being attached to the negative post I and the rod I to the post I. Therefore the rod 1 is the negative and the rod I the positive. At the base of each of these rods is a small nut f, by tightening which the plates N N and coils J J of the rheostat are held in position. Theplates N are of rubber or fibrous or other non-conducting material, and about one thirty-second of an inch in thickness and of about equal diameter with the switch-plate. These plates are placed between the rods I l at distances apart, and serve to hold annular coils J J in their positions. The plates N form layers of asbestus or other heat-resisting substance, and they, with the plates N, serve for preventing the overheating of the rheostat. In the open spaces between the plates the coils J, J, or J are inserted, the ends of the coils passing through the plates underneath, thence to the brass strips on the switch-plate. The rods I I are insulated to prevent short-circuiting by touching any of the coils, and they not only act as conductors, but also serve to bind the parts of the rheostat together. The respective pairs of plates N N should be placed at such distances from each other that the coils may be inserted between them and held in position without pressing them too closely, thus securing the necessary ventilation. By means of the nutsfthe plates and coils may be loosened at any time to facilitate the removal of damaged coils and the introduction of new ones.

My method of coiling the wire is shown plainly in either Fig. 5 or Fig. (3. I preferto adopt two approximately-elliptieal coils, as shown in Fig. 5, as the same will give greater ventilation, though perhaps the greater number of turns will more than counterbalance any advantage gained in this respect. Either method, however, can be used to advantage. It will be seen from the drawing that the first coil connects with strips K and K all the coils being in series and the last one connectthence by the rod I to the lamp.

ing with K and K and from K the current passes by fuse-wire K to the binding-post I, If desired, the last coil might be connected directly to the rod 1 but I prefer the arrangement shown, as it gives greater security against a possible heavy short circuit. The fuse-wire having a capacity of one ampere, would of course melt before the danger limitis reached. The coils not being wound on a spool or center rod, and being constructed as described, may be inserted either before or after 'the plates which hold them in position are applied on the rods 1 1 The binding-posts I and I are incased in hard rubber, which is an advantage over a binding-post constructed entirely of metal, as the switch can be moved from one side to the other without possibility of a short circuit, which cannot be done if the binding-posts are entirely of metal.

111 carrying out my invention I have used German-silver wire, double silk insulation. The two coils nearest the lamp were 2S-wire, the others 20, 30, 31, and 32, respectively. These coils were of such length as to cause a reduction in the current intensity of onetwentieth ampere per coil, thus causing a regular diminution of'light. The wire was cut into suitable lengths-say twenty five feet and coiled into double coils, as in Fig. 6, and during the coiling the wire was passed through a solution of shellac, and the shellac by adhering-to the wire served not only to increase the insulation, but also to render the coils solid and compact, so that they could be handled without possibility of becoming uncoiled. After coiling the wire it was again steeped in shellac and thereby thoroughlyinsulated, and when dry the coils were inserted between the plates, as before described. I do not confine myself to any specified thickness of plates or length of coils, as these may be varied in accordance with circumstances.

As the current quantity or intensity depends upon the electro-motive force divided by the resistance, the operation of my rheostat is simple and effective, and, if constructed substantially as herein described, all overheating will be avoided by the asbestus lining.

iVhen the within described combined socket and rheostat is in position with the light out, the switch-handle will have been turned to the right, the end of the switch-bar resting on the rubber or fibrous switch-plate, as shown in Fig. 3, and the circuit consequently broken. If the switch is moved so that it rests on the switch-strip K, circuit is at once established, the current passing from the positive binding-post H along the portion l? of the switch-bar to the contact-strip K, all the coils being thus in circuit and the current flowing in the direction of the arrows through each of the coils to the binding-post I, thence by the rod I to the lamp, as will be seen by following the direction of the arrows, and through the lamp to the negative rod 1 and thence to the negative binding-post I on Lil the switch-plate. Assuming the resistance of the lamp-filament to be two hundred ohms (when hot) and the electro-motive force in the main to be one hundred and ten volts, there would be a current-intensity of nearly 011eseventh ampere resulting from the combined resistance of the rheostat and the lamp. The lamp would therefore be burning at less than four-candle power. This applies to one hundred and ten volt siXteen-eandle-power lamps requiring from fifty to fifty-five watts. Rhee stats for lamps of higher power or less voltage can be supplied, the resistance of the coils being varied proportionately to the resistance of the lamp. As the switch-bar is moved to K the first coil is out out of the circuit, With a corresponding increase in the light until, when the switch rests on K the lamp is burning at its full power. The switch may be left for any desired length of time at a point which will give the desired intensity of light.

A leading novelty of my invention in addition to the combining of the socket with the wire coil rheostat lies in the facility with which the current intensity may be reduced to any desired extent by the insertion in series with the filament of the lamp of a variable number of coils of German-silver wire of suitable resistance.

My rheostat, by being constructed as herein described, need not be more than two inches in diameter and not more than four inches in length, and while it is thus compactit is simple in construction, easily wired, and can be manufactured as eheaplyasany good springsocket, and, being lined with asbestus or other heat-resisting material and having openings at each end of the outer case, is effective for the purpose designed, perfect ventilation being secured, and it is found that after burning for several hours, with every coil in circuit, it does not become hot enough to prevent its being grasped by the naked hand.

Socket-rheostats constructed in accordance with my invention are found to work advantageously to both the producer of electric lights and the consumer, for though the decrease in current will, by no means, be proportional to the decrease in light, owing to the amount of electrical energy expended in overcoming the resistance of the rheostat, yet Where the socket-rheostat is in general use it will be found there is a decided gainto wit, to the producerin the lifetime of the lamp, as the current is turned on by degrees instead of witha sudden rush, as in the spring-socket, in consequence of which the lamp-filament lasts longer and gives better results. Under my construction, should any coil become short-eircuited through defective insulation, it would not greatly impair the elfecieney of the rheostat, except in so far as that one coil is concerned, the other coils still remaining intact. If desired, an extra number of coils could be furnished ready for insertion at a cost of not more than a few cents per coil and damaged coils substituted by perfect ones at any time, and to do this an experienced wiringman would not be required, nor would it be necessary to take the rheostat all apart, but simply to remove the outer cylinder, loosen the nuts at the base of the rods and their proper binding-screws, and take out the damaged coil and insert a perfeet on e.

lVhat I claim as my invention is- 1. In a rheostat for independent or individual lamps, in combination, an outer case having a suspending cap and a foot-socket for an electric lamp, wire resistance-coils formed of wire wound spirally so as to form hollow sidewise-tight cylindrical chambers or central passages and applied and confined between non-conducting disks arranged upon insulated electrical conducting-rods having binding-posts at their upper ends, said coils and disks being arranged between the lamp-socket and the suspending cap, and means for electrically connecting the lamp and rheostat and making and breaking the circuit, substantially as described.

2. In a rheostat, in combination, an outer case having a suspending cap and a footsoeket for an electric lamp, asbestus or other suitable lining to the case, ventilation-pas sages at bottom and top of the case, resistance-coils formed of wire wound spirally so as to form hollow sidewise-tight cylindrical chambers and applied and confined between non-conducting disks arranged upon insulated electrical conducting-rods having binding-posts at their upper ends, said coils and disks being within the case and between the lamp-socket and the suspending cap, and means for electrically connecting the lamp and rheostat and making and breaking the circuit, substantially as described.

A rheostat comprising, in combination wire resistance-coils wound so as to form sidewise-tight cylindrical chambers or central passages through them, confining-disks of suitable non-conducting material, and insulated electric conducting-rods having binding-posts at their upper ends, substantially as described.

a. The combination of the rubber or fiber disks, asbestus disks beneath the rubber or fiber disks, annular wire coils, insulated elec trical conducting-rods, base-tie plate, nuts, switch-plate, insulated metal strips embedded in the switch-plate, the spring-switch having an operating-handle, binding-posts, and an outer case having ventilating-passages, a suspending cap, and a foot-socket for an electric lamp, and means for electrically connecting the lamp and rheostat and making and breaking the circuit, substantially as described.

5. In a rheostat, in combination, the resistance-coils formed of wire wound so as to form sidewise-tight cylindrical chambers, rubber or fiber disks applied upon insulated electrical conducting-rods, and an electrical lamp, and a suspending cap, a switch-plate,

ICO

switch-strips, and connecting-wires applied in series to the respective coils and strips, substantially as and for the purposes described.

(3. In a rheostat, in combination,resistancecoils of wire wound so as to form sidewisetight cylindrical chambers or central passages through the coils, a switch-plate of fiber or hard rubber or other non-conducting material, a series of brass strips embedded in the plate and insulated and arranged in a semicircle upon said plate, a binding-post for wire on each end of said semicircle of strips, a screw device surmounted by a binding-post for wire in the center, and a movable spring-switch vibrating on said screw device and connecting with said strips successively, substantially as described.

7. In a rheostat, in combination, a switchplate, a number of brass strips embedded and insulated in the plate, a movable switch connected at the center of the switch-plate by a screw device, the end of the switch adapted to be connected successively to the said brass strips and held in firm contact with said strips by a binding-nut on the screw device, and said screw device being surmounted by a binding-post for Wire, and a series of annular resistance-coils, non-conducting disks,

insulated electrical conducting rods, and means for electrically connecting the lamp and rheostat and making and breaking the circuit, substantially as described.

8. The combination of the annular resistance-coils, two insulated brass rods with binding-posts for wire at their upper ends and movable nuts at their lower ends, and a switch-plate, and means for electrically connecting the lamp and rheostat and making and breaking the circuit, substantially as described.

9. In a rheostat, the combination of the switch-plate, the brass rods, a series of ann ular resistance-coils, circular plates of fiber, hard rubber, or other non-conductor, circular plates of asbestus or other heat-resisting material, said pairs of plates being arranged at proper distances from each other on said brass rods so as to leave a space between each pair of plates for the insertion of the resistance-wire THOMAS A. LACEY.

Witnesses:

A. P. DAVIS, W. O. MOLEAN. 

